Buggy code:
public class ArgumentReader { String arguments ; int position ; Stack < Argument > currentArgumentStack ; CommandLibrary subcommandLibrary ; public ArgumentReader ( String arguments , CommandLibrary subcommandLibrary ) { } public ArgumentReader ( String arguments ) { } public class ArgumentException extends Exception { private static final long serialVersionUID = - 5322508080772813318L ; public ArgumentException ( String msg ) { } } public class ArgumentSyntaxException extends ArgumentReader . ArgumentException { private static final long serialVersionUID = - 9038854115751111790L ; protected Argument inArgument ; public ArgumentSyntaxException ( String msg , Argument arg ) { } public Argument inArgument ( ) { } } public class UnknownArgumentException extends ArgumentReader . ArgumentException { private static final long serialVersionUID = 2261534049445636858L ; protected String name ; public String getArgumentName ( ) { } public UnknownArgumentException ( String msg , String name ) { } } public void beginArgument ( Argument arg ) { } public void endArgument ( ) { } public void syntaxError ( String msg ) throws ArgumentReader . ArgumentSyntaxException { } public void unknownArgument ( String name ) throws ArgumentReader . UnknownArgumentException { <START_BUG> throw new ArgumentReader . UnknownArgumentException ( "Uknown<seq2seq4repair_space>argument<seq2seq4repair_space>name." , name ) ; <END_BUG> } public void unspecifiedRequiredArgument ( String name ) throws ArgumentReader . ArgumentException { } public char readChar ( ) throws ArgumentReader . ArgumentException { } public char tryReadChar ( ) throws ArgumentReader . ArgumentException { } public String readString ( int length ) throws ArgumentReader . ArgumentException { } public char peekChar ( ) throws ArgumentReader . ArgumentException { } public void back ( ) { } public boolean atEnd ( ) { } public void setPosition ( int p ) { } public int position ( ) { } public String getWholeArguments ( ) { } public void expect ( char c , String positionDescription ) throws ArgumentReader . ArgumentException { } public void expect ( String str , String positionDescription , boolean ignoreCase ) throws ArgumentReader . ArgumentException { } public void expect ( String str , String positionDescription ) throws ArgumentReader . ArgumentException { } public boolean tryExpect ( char c ) throws ArgumentReader . ArgumentException { } public boolean tryExpect ( String str ) { } public void skipWhitespace ( ) { } public Object readArgument ( Argument arg ) throws ArgumentReader . ArgumentException { } public Map < String , Object > readArguments ( List < Argument > args , Context ctx ) throws ArgumentReader . ArgumentException { } boolean replaceSubcommands = true ; public void deactivateSubcommands ( ) { } public void activateSubcommands ( ) { } public boolean subcommandsActivated ( ) { } public void setSubcommandLibrary ( CommandLibrary cl ) { } public CommandLibrary getSubcommandLibrary ( ) { } protected void replaceSubcommandHere ( ) throws ArgumentReader . ArgumentException { } }

Fix:
throw new ArgumentReader . UnknownArgumentException ( "Unknown<seq2seq4repair_space>argument<seq2seq4repair_space>name." , name ) ;